When a thin film and a substrate surface are planarized in a manufacturing process of an LSI device and so on, a chemical mechanical planarization method (CMP method) has been put to practical use. With miniaturization of an LSI device and reduction in the cost, there is required a CMP technique of processing a device surface into flatter, a lower level of defects, and more inexpensively.
In the CMP method, since slurry (polishing agent) containing polishing abrasive grains is used, there is a problem that scratches (polishing flaw) caused by abrasive grain residues cannot be prevented completely. Although the number of scratches and the size can be suppressed with improvement of the CMP method, with the miniaturization of the LSI device, in the future a construction of a several nm order is required to be processed without damage. For example, in a STI (Shallow Trench Isolation) process in LSI manufacture, a SiO2 film formed on the entire surface while covering a minute groove pattern is polished and removed without damage by the CMP method, and the SiO2 film is required to be embedded only in the groove. Since a transistor is formed on the polished surface, it is especially required to suppress scratches.
For the above problem, there has been known CMP temperature control as the CMP technique with high flatness, a low level of defects, and high productivity. In conventional CMP temperature control, air is jetted toward a polishing pad surface in CMP, and the pad surface and slurry on the surface are cooled. However, this method is cooling utilizing heat of vaporization of the slurry according to air blow, and the cooling capacity is insufficient.
Meanwhile, in order to suppress scratches, CMP is required to be performed after removing residues and foreign matters on the polishing pad. As a conventional removal method, a diamond dresser is pressed against the polishing pad surface between polishing operations, and the pad surface is scraped by approximately 1 μm and cleaned while flowing a cleaning liquid such as purified water. This cleaning is called dressing. The diamond dresser is a disk with a large number of minute industrial diamonds arranged on the surface. When diamond microparticles are dropped, this is a major cause of a large scratch. Although it is preferable to perform dressing in the CMP process in terms of productivity of LSI, the diamond microparticles may be dropped; therefore, dressing is performed between the polishing operations, and this interferes with the improvement of the productivity.
The polishing pad is generally formed of foamed polyurethane, and the pore diameter of a foam is several ten μm. Since a foam portion is exposed on the polishing pad surface, a myriad of pores with a depth of several ten μm appear on the pad surface. In order to enhance slurry retention capacity, a large number of vertical holes with a depth of several hundred μm are often formed in the pad surface. Thus, a large number of the pores with a depth of from several ten μm to several hundred μm are formed in the pad surface. Although the polishing pad surface can be cleaned by the diamond dresser, polish residues and foreign matters accumulated in a deep portion of each pore cannot be removed, and thus the polish residues discharged from the pores may cause scratches.